Elizabeth Griffin, a photographer at The Dr. Oz Show who snapped the precious photo, told NBC New York, "I'm not sure too many folks noticed because the baby was so fast asleep, but I've never seen anything like it. He kissed his head and kept running.

Ketchell explained what was happening in Runner's World on Tuesday, saying, "I wanted a way to honor him and everyone else affected by the syndrome. So I decided to run New York in his honor, to raise funds for others with the same circumstances."

Ketchell set out to break 3 hours, 21 minutes at the NYC Marathon to represent Wyatt's three copies of his 21st chromosome, something unique to those with Down syndrome. He teamed with LuMind Research, a charity for people who run to raise money for research on Down syndrome. His fundraising goal was $3,210. At last count it was over $11,700.

"I always wanted to carry Wyatt across the finish line, but I knew if I was going to break 3:21, it was going to be close and there wouldn't be enough time for that," he explained on Runner's World.

"After mile 20, when I was hiking it in, I texted my wife to tell her what happened and that I was coming for Wyatt. She had to fight to get near the finish line because the marathon is so big, about 50,000 competitors and so many spectators. She handed him over to me right at mile 26. And then I carried him across the line.

"To me, it was almost better than breaking 3:21. I had pushed my limits, which was the point. I couldn't go any farther. And we got to share the moment of going across the finish line together.

"I'm not really a crier, but tears were definitely starting to come. People around us were crying-even people who didn't know the story, who just saw me carrying my son across the line. Usually when you run a marathon, you put your name on your bib so everyone will cheer for you. I had put Wyatt's name on mine so people were screaming for Wyatt the whole time. That made things emotional from mile 1.

"When I was walking with him toward the finish line, everyone was still cheering his name. I told everyone, 'This is Wyatt,' and that made it so special."

The next day, Ketchell awoke to discover the photo of he and his son on social media, and his wife tracked down Griffin, thus leading to his explanation of the photo in Runner's World.

"We have had a long road," Marya Ketchell wrote to NBC New York. "Wyatt was born premature and spent the first 67 days of his life in the NICU. He has been through more in his seven months than most people go through in a lifetime, and he will be having open-heart surgery in April. He is the best, bravest person we know, and running the marathon for him was so important for our family."